X-ray image intensifier input phosphor screen and method of manufacture thereof

ABSTRACT

The surface of a waffle-like metal substrate forms an array of cells for the support for the input phosphor screen of an x-ray image intensifier tube. The hollow projecting walls of the metal surface substantially reduce degradation of image resolution due to lateral scattering of light in the phosphor and thereby permits use of a thicker phosphor screen for higher x-ray absorption and, or higher image resolution. The method of fabricating the phosphor screen includes the intermediate steps of forming rubber and plastic replicas of a metal master of the waffle surface. The plastic replicas are nickel plated to form low cost metal replicas with the plastic being dissolved whereby the projecting walls are hollow.

United States Patent 1191 [1 1 3,783,299 Houston Jan. 1, 1974 [54]X-RAYIMAGEINTENSIFIER INPUT 3,584,216 6/197! Tinney 250/80 PHOSPHORSCREEN AND METHOD OF MANUFACTURE THEREOF Primary Examiner-Archie R.Borchelt Arr J h F. Ah t a]. [75] Inventor: John M. Houston,Schenectady, omey O n em 57 ABSTRACT [73] Assignee: General ElectricCompany, The surface of a waffle-like metal substrate forms anSchenectady array of cells for the support for the input phosphor [22]Filed; May 17, 1972 screen of an x-ray image intensifier tube. Thehollow projecting walls of the metal surface substantially re- [2]] Appl254100 duce degradation of image resolution due to lateral scattering oflight in the phosphor and thereby permits 521 US. Cl. 250/483, 250/213VT, 250/486 use of a thicker p p Screen for higher y 51 Int. Cl. H01 jl/62 sorption and, or higher image resolution The method [58] Field ofSearch 250/80, 213 VT, 483, of fabricating the p p Screen includes theinter- 250/4 313 92 mediate steps of forming rubber and plastic replicasof a metal master of the waffle surface. The plastic repli- 5 R f rCited cas are nickel plated to form low cost metal replicas UNITEDSTATES PATENTS with the plastic being dissolved whereby the projectingwalls are hollow. 2,689,189 9/1954 Hushley 250/80 X 2,882,413 4/1959Vingerhoets 250/80 20 Claims, 8 Drawing Figures 7 "I: 9 70 """llllll'll,"

Pl/UJPl/OR 1" P. 6/ I i 1 i i i 1 5/1/00: 1 Pf 57/1 60 1 \i"" I 4/? /0a/////l //1 My invention relates to an x-ray image intensifier tube, andin particular, to the phosphor screen structure at the input end of thetube and method of manufacture thereof.

The x-ray image intensifier tube is especially useful in the medicalfield for obtaining brighter x-ray images, particularly the image ofbody organs which generally are of low contrast. Conventional xray imageintensifiers employ in the input thereof a uniform layer of a dense highatomic number phosphor for absorbing the incident x-rays which havetraversed through a patients body. The x.-ray photon is absorbed in thephosphor layer and light photons in the order of 1,000 light photons foreach x-ray photon are generated in the phosphor layer and emitted in alldirections from the point of x-ray photon absorption. A thinphotoemitting coating deposited on the surface of the phosphor layeremits photoelectrons in response to light photons incident thereof. Thephotelectrons are accelerated and electron-optically focussed onto asecond phosphor screen at the output end of the image intensifierresulting in a brighter image than at the input phosphor screen.

The thickness of the phosphor layer in conventional image intensifiersis typically 5 to 12 mils and is a compromise between a thick layernecessary for high x-ray absorption and a thin layer necessary for highimage resolution (a 12 mil thick layer yields a resolution of 40 to 50line pairs per inch), resolution and contrast degraded due to laterallight scattering within the phosphor layer. As a result, the typical5-l2 milv thickness phosphor layer in conventional x-ray imageintensifier tubes has a relatively low x-ray absorption in the order of15 to 40 percent of the incident rays. Obviously, it would be highlydesirable to employ a thicker phosphor layer in the input end of thex-ray image intensifier tube to thereby increase the x-ray absorption(and thus the sensitivity) but with less loss in resolution and localcontrast than occurs in conventional image intensifiers,

or alternatively, use aconventional thickness phosphor layer but withincreased reoslution.

Therefore, one of the principal objects of my invention is to provide anew and improved x-ray image intensifier tube having an input phosphorscreen which simultaneously can achieve both high x-ray absorption andhigh image resolution, and the method of manufacture thereof.

Another object of my invention is to providea relatively thick inputphosphor screen with means to substantially reduce degradation ofresolution and local image contrast due to lateral light scattering inthe phosphor and the method of manufacture thereof.

A further object of my invention is to provide a low cost fabricationprocess for manufacturingiithe improved input phosphor screen.

Briefly stated, and in accordance with my invention, I provide an x-rayimage intensifier input phosphor screen wherein a phosphor layer isdeposited in the cells formed by hollow wall-like projections on thesurface of a waffle-like reflective metal substrate. The cells form anarray of equal size squares or hexagons and the phosphor layer extendsoutward slightly beyond the ends of the metal wall projections. Theother side of the metallic substrate, which contains indentationscorresponding to the opposite side wall projections, is bonded to thex-ray image intensifier tube face plate which may be formed of glass ora low atomic number metal such as aluminum. The outer surface of thephosphor layer, spaced from the metallic substrate, is smooth andsubstantially parallel to the majorsurface of the face plate and a thinfilm of a photoemitter material is deposited thereon. The phosphor layercan be relatively thick and thus obtain increased sensitivity and themetallic cell walls substantially reduce degradation of image resolutionand contrast due to lateral scattering of light in the phosphor.

My x-ray image intensifier input phosphor screen is fabricated by thefollowing method. Sheets of metal mesh are formed by photoetching thinmetal sheets to produce an array of small holes in the mesh having asquare or hexagonal shape. The sheets of metal mesh are superimposed inprecise hole alignment and diffusion bonded to a heavy planar metalsubstrate to thereby obtain a waffle-like surface wherein the wallprojections which define an array of cells are each approximately 1.5 to2 mil wide and the cell width is about 4 to 5 mils. The walls of thecells are then thinned to approximately 0.5 mil width by chemicaletching and this metal substrate having a waffle-like surface is used asa master from which silicone rubber replicas are made. Each siliconerubber replica has the wall indentation surface thereof coated with asuitable plastic material and such coated surface is drawn toward asupport member having the concave-shape of the x-ray image intensifierface plate. Upon hardening of the plastic, the silicone rubber replicais removed, and the concave-shaped plastic structure has the wall-likeprojections of the metal master. The plastic replica is treated to beelectrically conductive, and is electroplated to form a very thin, highlight reflectivity, metal layer on the surface thereof. The plasticmaterial is then dissolved leaving the metallic replica which istransferred to the face plate of the image intensifier tube and bondedto the inner surface thereof. The array of cells formed by the hollowwall projections of the metallic replica are then filledwith a phosphormaterial which extends slightly beyond the ends of the projecting wallsand forms a smooth outer surface upon which a thin uniform coating of aphoto-emitter material is deposited to form the photocathode of thex-ray image intensifier tube.

The features of my invention which I desire to protect herein arepointed out with particularity in the appended claims. The inventionitsellf, however, both as to its organization and method of operation,together with further objects and advantages thereof may best beunderstood by reference to the following description taken in connectionwith the accompanying drawings wherein like parts in each of the severalfigures are identified by the same reference character, and wherein:

FIG. 1 is an elevation sectional view of a conventional x-ray imageintensifier tube;

FIGS. 2a and 2b are top views of two geometries of an array of cellsformed by the waffle-like surface on a metallic substrate utilized infabricating a master in accordance with my invention;

FIG. 3 is an elevation sectional view of bonded sheets of metal meshwhich form the waffle-like surface illustrated in FIGS. 2a, 2b, but to alarger scale, and also indicates the thinned walls of the cellsoccurring after a subsequent etching process;

FIG. 4 is an elevation sectional view, to the same scale of FIG. 1, of asilicone rubber replica of the master illustrated partially in FIG. 3,and also shows a concave support member onto which the silicone rubberreplica is pressed to form a plastic replica;

FIG. 5 is an elevation sectional view of the plastic replica formed onthe support member in FIG. 4, and also shows a thin metal layer platedon a first part of the plastic replica to form a metallic replica, andthe silicone rubber replica being peeled from the plastic replica;

FIG. 6 is an elevation sectional view, to a larger scale than FIG. 5, ofthe metallic replica formed in FIG. 5 and bonded to the x-ray imageintensifier tube face plate, and a phosphor layer deposited on themetallic replica waffle surface; and

FIG. 7 is an elevation sectional view, of the input end structure of myimage intensifier tube as shown in FIG. 6 after the phosphor surface hasbeen smoothed and a photoemitter coating deposited thereon.

Referring now in particular to FIG. 1, there is shown a conventionalx-ray image intensifier tube comprised of a glass envelope 10 having aninput end (face plate) 100 which has a uniform phosphor layer 11 ofthickness in the range of 0.005 to 0.012 inch deposited on the innersurface thereof. The phosphor may be zinc cadmium sulfide or cesiumiodide as typical materials onto which a thin film 12 of photoemittermaterial is deposited of thickness of approximately 100 Angstroms. Thephotoelectrons emitted by the photoemitter coating 12 are focussed byelectrode 13a maintained at a potential of several hundred volts and areaccelerated to approximately 25 kilovolts by means of electrode 13!;(connected to a suitable DC. voltage source) at the output end of theimage intensifier tube, the electrodes being suitably shaped to provideelectron-optical focussing of the accelerated photoelectrons onto asecond uniform phosphor screen (layer) 14 deposited on the inner surfaceof the glass envelope at the output end 10b thereof. The image appearingon the second phosphor screen 14 is a brighter version of the image onthe first phosphor screen 11 and can be viewed directly by the physicianor be subjected to further processing. The paths of two photoelectronsbetween the photoemitter coating 12 and the second phosphor screen 14are indicated by dashed line and arrowheads. As stated hereinabove, thethickness of the input phosphor screen 11 in conventional x-ray imageintensifier tubes is a compromise between a thick screen for high x-rayabsorption and thin screen for high resolution which is determinedprimarily by lateral light scatter in the phosphor.

My invention provides a new and improved high resolution x-ray imageintensifier input phosphor screen which avoids the compromise betweenthe thick and thin phosphor screen by the use of a waffle-like metallicsurface wherein hollow wall projections thereof substantially preventdegradation of resolution and local image contrast due to lateralscattering of light in the phosphor. My invention-permits the use of athicker phosphor screen for achieving higher x-ray absorption withoutthe attendant degradation of resolution and contrast obtained inconventional image intensifiers, or a phosphor screen of conventionalthickness but with a significantly higher resolution. The waffle-likemetallic surface could be achieved by forming the wall projections whichdefine an array of cells of the waffle pattern, by separation wireelements, however, since it is desired to obtain cells of very smallsize, in the order of 5 mil width, and have a plurality of such cells ofidentical size, the fabrication process to be described hereinafter isbelieved more suitable for providing the consistently equal size cellsand projecting walls.

This invention is distinguished in at least the following five respectsfrom a related invention described and claimed in my concurrently filedpatent application Ser. No. 254,099 wherein wall-like projections of awaffle-like substrate are (1) solid, the entire substrate is (2) arelatively thick (3) layer having a completely smooth surface and ismade of (4) a silicone resin and granular phosphor mixture, and (5) doesnot require an additional intermediate step in fabrication to produce aplastic replica on which the final replica is formed.

The fabrication process is initiated by selecting sheets of metalsuitable for photoetching such as nickel or stainless steel in the orderof l or 2 mils thick. This relatively small thickness is chosen since itis easier and more precise to photoetch holes with a depth at least afactor of two smaller than-the hole diameter. An identical pattern(array) of holes is etched through each sheet. The etched holes in themetal mesh sheets preferably have a square or hexagonal shape asillustrated in FIGS. 2a and 2b, respectively, with a center-tocenterhole spacing of approximately 6 mils and separation (wall thickness) ofapproximately 1.5 to 2 mil as indicated on the drawing. The holes are ofequal size and equally spaced from each other and form an array ofidentical rows and columns of holes to maximize the hole area in themesh. Other shape holes, such as triangular or circular could be used,however, such shaped holes produce less open area in the mesh.

Upon completion of the photoetching step, the sheets of metal mesh aresuperposed in precise hole alignment to form an assembly ofapproximately 10 mils height as one example, the sheets of metal mesh30, 31, 32

and 39 being stacked on a heavy planar substrate 40 v of the same metalas the meshand subsequently being diffusion bonded thereto. Theapproximately 10 mil thick stack of metal mesh is diffusion bonded bybolting the mesh assembly between two massive planes of metal, the upperone of which is thinly coated with an oxide such as MgO to preventsticking, and this assembly is heated to a suitable temperature (e.g.,approximately 1,000C when bonding nickel or stainless steel) in ahydrogen atmosphere or vacuum to accomplish the diffusion bonding. Thediffusion bonding results in a waffle-like structure having a surfaceillustrated by the heavy solid line in FIG. 3 wherein the projectingwalls 41, 42, 43 from the surface of substrate 40 are rectangular in thesection taken vertically through the projecting walls. The space betweenthe surrounding walls and substrate 40 will be hereinafter described asa cell and it is obvious that the diffusion bonding step results in aplurality of identical walls wherein FIG. 2a or FIG. 2b represent thetop view of the cell structure shown in elevation sectional view in FIG.3. The walls 41, 42, 43 of the cells and then thinned to approximately0.5 mil thickness by a chemical etching process to produce the mastersubstrate structure indicated by dashed line in FIG. 3. The thinnedwalls are substantially thinner than the corresponding thinned wallsdescribed in my aforementioned concurrently filed application Ser. No.254,099 since the metal that forms such hollow walls in the finalstructure is merely lightreflective and does not generate light photonswhereas in Ser. No. 254,099 such walls are solid and the granularphosphor portion thereof is both light-reflective and generates its ownlight which contributes to the light generated in the adjacent phosphorlaser.

The array of cells formed by the waffle-like surface of the metal masterstructure in FIG. 3 after the chemical etching process could be filledwith a phosphor material to form a phosphor screen, however, the processhereinabove described is relatively expensive and in accordance with myinvention, I fabricate many inexpensive metal replicas of such originalmaster whereby the cost per x-ray intensifier tube will be small. Also,at some stage in the process it is necessary to sag the planar surfaceof substrate 40, that is, to obtain it in a concave-shaped conforming tothe shape of the face plate a of the image intensifier tube.

In order to replicate the master illustrated in FIG. 3, an intermediatestep of making one or more silicone rubber replicas is utilized. Thesilicone rubber replica is fabricated by vacuum impregnation wherein themaster is convered with a layer of liquid silicon rubber (e.g., GeneralElectric RTV-l l) to which a small amount of a suitable curing catalysthas been added. The coated master is then placed in a vacuum chamber fora few minutes in order to pump away all air bubbles and insure that thesilicon rubber contacts all the crevices of the master. The rubber isthen allowed to cure for an appropriate period, e.g., 24 hours, in orderto form an elastic, rubbery solid. The silicone rubber replica isapproximately 50 mils thick in order toregngin somewhat flexible so thatit can be subsequently easily removed by peeling from a plastic replicato be described hereinafter.

Referring now to FIG. 4, a support dish member 44 which has the sameconcave form as face plate 10a of the image intensifier tube is utilizedas a form on which to fabricate a plastic replica of the FIG. 3chemically etched waffle-like metal surface. The support form 44 may bemade of virtually any material which is chemically inert to the plasticmaterial and its solvent, glass or stainless steel being two typicalmaterials. A suitable plastic material which readily hardens at roomtemperature, or at a slightly elevated temperature, such as polymethylmethacrylate (Lucite) or an epoxy resin such as Hysol R8-2038 in themolten state is coated along the wall indented side 45a of the rubberreplica 45. The two margins 45b, 0 along the wall indented side 45a ofthe rubber replica are suitably retained against corresponding planarmargins of the concave support dish 44 and the entire assembly is placedwithin a chamber wherein a vacuum is drawn between the rubber replica 45and support dish 44 thereby pressing the rubber replica toward theconcave form to produce a plastic replica 46 of the FIG. 3 masterwaffle-like surface except that the plastic replica is curved into theconcave shape of the image intensifier tube face plate 10a rather thanbeing planar, as shown in part in FIG. 4.

Upon hardening of the plastic, the silicone rubber replica 45 is removedtherefrom by peeling it from the plastic replica 46 as shown in FIG. 5,and the rubber replica may be reused to form additional plasticreplicas. The plastic replica 46 is made electrically conductive byevaporating an electrically conductive thin metal coating (of silver,gold or copper as three typical examples) onto the plastic surface.Alternatively, the plastic is rendered electrically conductive by mixingthe metal or graphite in powder form into the liquid plastic such thatthe plastic has bulk conductivity. After the plastic replica has beenrendered electrically conductive, a very thin layer 50 (of thickness inthe range of 0.2 to 0.5 mil) of a suitable metal such as nickel or othermetal having relatively high light reflectivity is electroplated ontothe plastic surface.

The plastic material is then dissolved in a suitable solvent such asacetone for the Lucite or Hysol dissolver AC-4079 for the Hysol plasticand the remaining metallic replica 50 is carefully transferred to theinner surface of the concave-shaped face plate 10a of the x-ray imageintensifier tube and positioned thereon. The face plate 10a isfabricated of glass or a low atomic number metal such as aluminum.

The metal replica 50 is bonded to the face plate 10a by means of a thincoating 60 of silicone resin as one example to form the structureillustrated in FIG. 6 wherein the hollow wall projections of the metalreplica extend normal to the surface of face plate 10a. The array ofcells formed by the metal waffle-like surface are filled with a suitablepreferably transparent phosphor material using conventional techniques,the phosphor layer extending beyond the ends of the wall projections ofthe metal replica 50. The phosphor 61 can be a conventional granularphosphor (but of large grain size to obtain high light transmissioncharacteristics) such as silver-activated zinc cadmium sulfide without,or in a silicone resin binder, or, more desirably is a transparentphosphor such as evaporated cesium iodiode (CsI) phosphor. Evaporationof the CsI from vertically above the metal replica 50 results in theouter surface of the phosphor layer 61 having the undulating form 61ashown in FIG. 6 due to the projecting walls of the metal replica. Theuneven surface 61a of the phosphor outer surface is mechanicallypolished in a dry box, since CsI is a relatively soft material, toobtain the smooth surface 61b shown in dashed line. If the indulationsare not so severe as to upset either the electron-optics or theformation, and or surface resistivity of the photocathode (to bedescribed hereinafter), then it may not be necessary to smooth out suchundulations. The phosphor layer is approximately 12 mils thick as onetypical example, and obviously can be made thicker if higher x-rayabsorption is desired. Large phosphor grain size herein is defined asparticle diameter greater than 0.3 mil.

Referring now to FIG. 7, a thin uniform coating of a suitablephotoemitter material is deposited on the smooth surface 61b of thephosphor layer 61 during the evacuation of the image intensifier tube toform the photocathode of such image intensifier tubeQThe photoemittermaterial may be of the common types known as 8-20 (a compound ofantimony, cesium sodium and potassium) or 5-11 (a compound of cesium,antimony and oxygen) as two typical examples and is a very thin coatingin the order of Angstroms. If desired, an isolating layer of transparentalumina, as one example, may be deposited between the phosphor 61 andphotoemitter 70 layers in order to isolate the alkali metal of thephotoemitter material from the phosphor, however, such isolating layeris not essential to the successful operation of my input phosphorscreen.

The light reflectivity of the metal replica surface is generallysufficiently high, but can be increased, if desired, by bright-dippingthe metal replica (i.e., immersing the replica for a moment in asolution of nitric acide, sulfuric acid and NaCl or by coating it withMgO smoke obtained by burning magnesium. The reflectivity of the metalreplica wall projections is not too critical since the height todiameter ratio of each cell is only slightly greater than unity.

The wall-like projections of the metal replica 50 extend normallythrough at least 50 percent of the phosphor layer 61 thickness, and asshown in FIGS. 6 and 7, typically extend through approximately 80percent of the phosphor layer. The effect of the relatively highlight-reflective wall projection surfaces is to substantially reducelateral scattering of light in the phosphor and thereby substantiallyreduce degradation of image resolution and contrast due to such cause.Obviously, the metal master can be made with more sheets of the metalmesh to thereby obtain a metal replica having wall projections ofgreater height whereby a thicker phosphor layer can be utilized forincreased x-ray absorption, and thus increased sensitivity, or, the samethickness phosphor layer can be used and the further extending wallprojections further improve the resolution. It should also be noted thatthe base portion of the metal replica (i.e., the floor portion of eachcell which interconnects the hollow wall projections), being fabricatedof a light-reflective metal, provides a means for reflecting lightphotons which are originally emitted toward the face plate 10a, backtoward the photoemitter layer 70. Thus, a separate light-reflectivecoating between the face-plate 10a and phosphor layer 61 is not requiredin my invention, although it is generally utilized in conventional x-rayimage intensifiers.

As stated hereinabove, the silicone rubber replica 45 is changed fromits original planar shape (on the nonindented major surface 45d thereof)into the desired concave shape conforming to the face plate surface.Alternatively, the final electroplated metal replica 50 is relativelyflexible due to its thinness and corrugated (hollow wall projections)form and therefore all of the replication including the electroplatedmetal replica) can be accomplished using planar geometry and the finalmetal replica can then be sagged into the desired concave shape whilebonding such replica to the face plate thereby simplifying the processof fabricating the plastic replica.

From the foregoing description, it is apparent that my invention attainsthe objectives set forth and makes available a new and improved x-rayimage intensifier tube which has an input phosphor screen thatsimultaneously achieves both high x-ray absorption (and thus highsensitivity) and high image resolution as well as providing a method ofmanufacturing such input phosphor screen. The method of manufacturingthe input phosphor screen is a low cost fabrication process due to theuse of a silicone rubber replica which permits fabrication of manyinexpensive metal replicas of the original master. The light-reflectivesurfaces of the hollow projecting walls of the metal replica preventdegradation of image resolution and contrast due to lateral scatteringof light in the phosphor layer and thereby avoid phosphor layerthickness compromise in conventional x-ray image intensifier tubesbetween high x-ray absorption and high imageresolution. It will beapparent to those skilled in the art that the waffle-like surface on themetal replica which constitutes the essence of my invention may takeother forms than that specifically illustrated and described above.Also, the support for the input phosphor screen, herein described as theface plate, may be slightly spaced from the input window of the tubeglass envelope. Thus, it is to be understood that changes may be made inthe particular embodiment of my invention as described which are withinthe full intended scope of the invention as defined by the appendedclaims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An improved x-ray image intensifier input phosphor screen comprisinga concave-shaped face plate of uniform thickness forming a support forthe input phosphor screen of an x-ray image intensifier tube, a metallicsubstrate member having hollow wall-like projections extending normal tothe inner surface of said face plate and outward in a direction awaytherefrom to form a waffle-like surface on a first major side thereof, asecond major side of said metallic substrate member having a majorportion of its surface parallel to the inner surface of said face plateand connected thereto, the remaining portion of said second side havingindentations corresponding to the hollow wall-like projections on saidfirst side, the first side of said metallic substrate member havingfloor portions interconnecting the wall-like projections to define thewaffle-like surface, the floor portions being parallel to the majorportion of the second side such that the metallic wubstrate member is asingle layer of the metal, phosphor layer deposited in cells formed bythe waffle-like surface on the first side of said metallic substratemember and being of sufficient thickness to extend slightly beyond theouter ends of the wall-like projections thereof to form a second surfaceconcave-shaped and substantially parallel to the inner surface of saidface plate, and means deposited on the second surface of said phosphorlayer for producing emission of photoelectrons therefrom in response tox-ray photons passing through said face plate and being converted tolight photons in the phosphor layer, the waffle-like surface of saidmetallic substrate member having a relatively high light reflectivityfor directing the light photons generated in the phosphor layer towardthe photoelectron producing means, the wall-like projectionssubstantially reducing degradation of image resolution and contrast dueto lat eral scattering of the light in the phosphor layer therebypermitting use of a thicker phosphor layer for higher x-ray absorptionand resultant higher sensitivity and, or, for obtaining higher imageresolution.

2. The x-ray image intensifier phosphor screen set forth in claim 1wherein the metallic substrate member layer is of thickness in the rangeof 0.0002 to 0.0005 inch.

3. The xray image intensifier input phosphor screen set forth in claim 1wherein said metallic layer is formed of nickel.

4. The x-ray image intensifier input phosphor screen set forth in claim3 wherein the major portion of the second side of said metallicsubstrate member is connected to the inner surface of said face plate bymeans of a thin uniform thickness layer of silicone resin for bondingthe adjoining surfaces. 5. The x-ray image intensifier input phosphorscreen set forth in claim 1 wherein said face plate is fabricated ofaluminum. 6. The x-ray image intensifier input phosphor screen set forthin claim 1 wherein said face plate is fabricated of glass. 7. The x-rayimage intensifier input phosphor screen set forth in claim 1 whereinsaid face plate is fabricated of a low atomic number metal. 8. The x-rayimage intensifier input phosphor screen set forth in claim 1 whereinsaid phosphor layer comprises cesium iodide. 9. The x-ray imageintensifier input phosphor screen set forth in claim 1 wherein saidphosphor layer comprises a transparent phosphor material. 10. The x-rayimage intensifier input phosphor screen set forth in claim 1 whereinsaid phosphor layer comprises a granular phosphor of large grain size ofparticle diameter greater than 0.3 mil to thereby obtain high lighttransmission characteristics. 1 l. The x-ray image intensifier inputphosphor screen set forth in claim 1 wherein the floor portions on thefirst side of said metallic substrate member each being square shaped.12. The x-ray image intensifier input phosphor screen set forth in claim1 wherein the floor portions on the first side of said metallicsubstrate member form equal size squares separated by equal size saidwall-like projections. 13. The x-ray image intensifier input phosphorscreen set forth in claim 1 wherein the floor portions on the first sideof said metallic substrate member each being hexagon shaped. 14. Thex-ray image intensifier input phosphor screen set forth in claim 1wherein Y the floor portions on the first side of said metallicsubstrate member form equal size hexagons separated by equal size saidwall-llike projections. 15. The x-ray image intensifier input phosphorscreen set forth in claim 1 wherein the wall-like projections eachextend outward approximately lO mils. 16. The x-ray image intensifierinput phosphor screen set forth in claim 1 wherein the wall-likeprojections each have an outer width di mension of approximately 0.5mils. 17. The x-ray image intensifier input phosphor screen set forth inclaim 1 wherein the floor portions on the first side of said metallicsubstrate member each have a width dimension of approximately 5 to 6mils. 18. The x-ray image intensifier input phosphor screen set forth inclaim 14 wherein the hexagon shaped floor portions each having a widthdimension of approximately 5 to 6 mils. 19. The x-ray image intensifierinput phosphor screen set forth in claim [wherein the wall-likeprojections of said metallic substrate member extend into the phosphorlayer at least halfway therethrough. 20. The x-ray image intensifierinput phosphor screen set forth in claim 1 wherein the wall-likeprojections of said metallic substrate msm sr ts th qushaiaprqximatsl%.9f h phosphor layer.

2. The x-ray image intensifier phosphor screen set forth in claim 1wherein the metallic substrate member layer is of thickness in the rangeof 0.0002 to 0.0005 inch.
 3. The x-ray image intensifier input phosphorscreen set forth in claim 1 wherein said metallic layer is formed ofnickel.
 4. The x-ray image intensifier input phosphor screen set forthin claim 3 wherein the major portion of the second side of said metallicsubstrate member is connected to the inner surface of said face plate bymeans of a thin uniform thickness layer of silicone resin for bondingthe adjoining surfaces.
 5. The x-ray image intensifier input phosphorscreen set forth in claim 1 wherein said face plate is fabricated ofaluminum.
 6. The x-ray image intensifier input phosphor screen set forthin claim 1 wherein said face plate is fabricated of glass.
 7. The x-rayimage intensifier input phosphor screen set forth in claim 1 whereinsaid face plate is fabricated of a low atomic number metal.
 8. The x-rayimage intensifier input phosphor screen set forth in claim 1 whereinsaid phosphor layer comprises cesium iodide.
 9. The x-ray imageintensifier input phosphor screen set forth in claim 1 wherein saidphosphor layer comprises a transparent phosphor material.
 10. The x-rayimage intensifier input phosphor screen set forth in claim 1 whereinsaid phosphor layer comprises a granular phosphor of large grain size ofparticle diameter greater than 0.3 mil to thereby obtain high lighttransmission characteristics.
 11. The x-ray image intensifier inputphosphor screen set forth in claim 1 wherein the floor portions on thefirst side of said metallic substrate member each being square shaped.12. The x-ray image intensifier input phosphor screen set forth in claim1 wherein the floor portions on the first side of said metallicsubstrate member form equal size squares separated by equal size saidwall-like projections.
 13. The x-ray image intensifier input phosphorscreen set forth in claim 1 wherein the floor portions on the first sideof said metallic substrate member each being hexagon shaped.
 14. Thex-ray image intensifier input phosphor screen set forth in claim 1wherein the floor portions on the first side of said metallic substratemember form equal size hexagons separated by equal size said wall-likeprojections.
 15. The x-ray image intensifier input phosphor screen setforth in claim 1 wherein the wall-like projections each extend outwardapproximately 10 mils.
 16. The x-ray image intensifier input phosphorscreen set forth in claim 1 wherein the wall-like projections each havean outer width dimension of approximately 0.5 mils.
 17. The x-ray imageintensifier input phosphor screen set forth in claim 1 wherein the floorportions on the first side of said metallic substrate member each have awidth dimension of approximately 5 to 6 mils.
 18. The x-ray imageintensifier input phosphor screen set forth in claim 14 wherein thehexagon shaped floor portions each having a width dimension ofapproximately 5 to 6 mils.
 19. The x-ray image intensifier inputphosphor screen set forth in claim 1 wherein the wall-like projectionsof said metallic substrate member extend into the phosphor layer atleast halfway therethrough.
 20. The x-ray image intensifier inputphosphor screen set forth in claim 1 wherein the wall-like projectionsof said metallic substrate member extend through approximately 80% ofthe phosphor layer.